Commit 6cfcd6f0 authored Jan 03, 2020 by Ard Biesheuvel Committed by Ingo Molnar Jan 10, 2020

efi/x86: Re-disable RT services for 32-bit kernels running on 64-bit EFI



Commit a8147dba ("efi/x86: Rename efi_is_native() to efi_is_mixed()")
renamed and refactored efi_is_native() into efi_is_mixed(), but failed
to take into account that these are not diametrical opposites.

Mixed mode is a construct that permits 64-bit kernels to boot on 32-bit
firmware, but there is another non-native combination which is supported,
i.e., 32-bit kernels booting on 64-bit firmware, but only for boot and not
for runtime services. Also, mixed mode can be disabled in Kconfig, in
which case the 64-bit kernel can still be booted from 32-bit firmware,
but without access to runtime services.

Due to this oversight, efi_runtime_supported() now incorrectly returns
true for such configurations, resulting in crashes at boot. So fix this
by making efi_runtime_supported() aware of this.

As a side effect, some efi_thunk_xxx() stubs have become obsolete, so
remove them as well.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Matthew Garrett <mjg59@google.com>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20200103113953.9571-4-ardb@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent bc7c9d62

arch/x86/include/asm/efi.h

+2 −16

Original line number	Diff line number	Diff line
		@@ -163,10 +163,10 @@ static inline bool efi_is_mixed(void)

		static inline bool efi_runtime_supported(void)
		{
		if (!efi_is_mixed())
		if (IS_ENABLED(CONFIG_X86_64) == efi_enabled(EFI_64BIT))
		return true;

		if (!efi_enabled(EFI_OLD_MEMMAP))
		if (IS_ENABLED(CONFIG_EFI_MIXED) && !efi_enabled(EFI_OLD_MEMMAP))
		return true;

		return false;
		@@ -176,7 +176,6 @@ extern void parse_efi_setup(u64 phys_addr, u32 data_len);

		extern void efifb_setup_from_dmi(struct screen_info si, const char opt);

		#ifdef CONFIG_EFI_MIXED
		extern void efi_thunk_runtime_setup(void);
		extern efi_status_t efi_thunk_set_virtual_address_map(
		void *phys_set_virtual_address_map,
		@@ -184,19 +183,6 @@ extern efi_status_t efi_thunk_set_virtual_address_map(
		unsigned long descriptor_size,
		u32 descriptor_version,
		efi_memory_desc_t *virtual_map);
		#else
		static inline void efi_thunk_runtime_setup(void) {}
		static inline efi_status_t efi_thunk_set_virtual_address_map(
		void *phys_set_virtual_address_map,
		unsigned long memory_map_size,
		unsigned long descriptor_size,
		u32 descriptor_version,
		efi_memory_desc_t *virtual_map)
		{
		return EFI_SUCCESS;
		}
		#endif /* CONFIG_EFI_MIXED */


		/* arch specific definitions used by the stub code */

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